Top: In Los Angeles's Hyde Park neighborhood, buckled, cracked sidewalks such as this were a common eyesore. Photos: George Gonzalez

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Tree roots can turn a city sidewalk into an impassable mess of broken-up concrete.

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Sidewalks and trees are often-overlooked assets. Los Angeles chief forester George Gonzalez believes both are just as much a part of a city's infrastructure as a road, a water main, or a sewage pipe—but most cities don't realize the true worth of either. He thinks it's high time they did.

A Walk On The Green Side

Los Angeles has about 700,000 street trees stretched across 465 square miles; with more than 1000 different species, Gonzalez is charged with maintaining both the largest and most diverse tree population in the country. He also maintains the city's 10,000 miles of sidewalks—again, the most in the United States. It's a big job, but Gonzalez—a certified municipal specialist with the International Society of Arboculture and frequent lecturer on tree-and sidewalk-management issues—knows it's important, based on the role sidewalks and trees play in a city's culture.

According to Gonzalez, a thriving urban forest adds value to a municipality by:

Increasing water quality: A tree filters rainwater, and it reduces soil erosion and runoff by absorbing stormwater.

Boosting property values: Trees make the houses on a street more desirable to prospective buyers.

Increasing the “feel-good” quotient: Community beautification, civic pride, and other benefits are less tangible but still worth considering.

Also, sidewalks let pedestrians travel to and from residences, businesses, schools, and other establishments. Neighborhoods without them experience significantly higher numbers of vehicle-pedestrian collisions, so their contribution to a neighborhood's safety is crucial.

Los Angeles might have a reputation as being the city that drives everywhere, but Gonzalez says that's not so. “L.A. is really a large city made up of many small communities and neighborhoods,” he says. “Many Angelinos rarely venture outside of their neighborhoods, and within our neighborhoods you'll find as much pedestrian traffic as you would in other large cities.”

Planning For Peaceful Coexistence

Unfortunately, trees and sidewalks often are at odds. One can cause damage to the other, thanks in part to poor planning.

“Trees historically have been treated as an amenity—something nice to look at, but not a vital infrastructure element,” he says. “They're often that last thing considered when planning a development. Not a lot of forethought is given to how trees coexist with neighboring infrastructure elements.”

Most often, a tree's closest “neighbor” is a sidewalk. However, Gonzalez says sidewalk design frequently doesn't take trees into account. Only recently have municipalities begun being diligent about planting the right tree in the right place. Even so, most of the time trees are not allowed adequate space to grow, so foresters are stuck with planting smaller trees, which provide less benefit.